1. Field of the Invention
The present invention relates to a technique of producing a photomask used for manufacturing a semiconductor device. In particular, the present invention relates to a mask defect inspection data generating method for generating inspection data used for a shape defect inspection process, and to a mask defect inspection method using inspection data obtained by the foregoing method.
In addition, the present invention relates to a mask production method including a process of inspecting defect using a mask defect inspection method.
2. Description of the Related Art
A photomask used for manufacturing a semiconductor device has the following problem. Specifically, with advance in pattern scale reduction, it is difficult to detect a microdefect formed on a mask. In order to detect the microdefect, inspection is required using high inspection sensitivity. For this reason, the inspection time becomes longer compared with the conventional case, and thus, inspection throughput decreases. In addition, a pattern forming region becomes wider compared with the conventional case; for this reason, an increase of inspection time by inspection area enlargement is also one of the problem.
The photomask defect inspection has the following two cases. One is the case of inspecting the entire surface of a pattern forming region. Another is the case of inspecting a specified area in the pattern forming region. The latter case is called an area limited inspection. In the actual mask defect inspection, the foregoing inspection method is employed. Besides, the following inspection method is employed. According to the inspection method, an area having defects allowable in the inspected area is previously defined as an inspection excluded area. If a defect detected in inspecting the entire surface of the pattern forming region or an area limited inspection area exists within the inspection excluded area, the defect is not counted as a defect.
The present defect inspection is made in combination with the foregoing methods. For example, according to die to database, when the area limited inspection and the area excluded inspection are made, coordinate information of a previously inspected area and an area excluding inspection is defined in inspection layout data. An inspection apparatus makes a defect inspection according to the area information defined in the data to determine whether or not a defect exists on a mask. The foregoing die to database detects a defect in the following manner. Specifically, a comparison is made between the following two data images, and thereby, the different portion between two data images is defined as a defect. One is a data image (sensor data) generated by capturing a pattern image formed on a photomask using a CCD camera of the inspection apparatus. Another is a data image (reference data) generated from design data.
The foregoing inspection methods have the following advantages. Namely, the specified area only is inspected, and partial areas in the inspection area are given as an inspection excluded area. However, the inspection apparatus makes an inspection according to the following operation. Specifically, the inspection apparatus continuously moves a designated area with an inherent stripe width of the apparatus in the X direction while repeating step movement in the Y direction. For this reason, a stripe turn is generated at the inspection area end in the X direction. The foregoing turn is a factor of temporarily stopping continuous movement. Therefore, the turn becomes much by setting an inspection excluded area, and thereby, the inspection time becomes long by the increased turn. As a result, the inspection time becomes remarkably long depending on an area setting method, and this is a problem of reducing throughput.